Particulate debris from friction components of a braking system, for example the rotors or drums and the pads or shoes, are typically generated during braking and released to the environment. Because of the chemical compositions typically employed in the friction components of braking systems, this particulate debris can include constituents, including but not limited to copper, cadmium, lead, mercury, and the like, that are known or suspected to have harmful effects when found in significant quantities in the environment.
Various regulations and laws intending to reduce potential negative environmental impacts of this particulate debris are either under consideration or in the process of passing in the legislatures of one or more U.S. states. These regulations and laws generally place limits on the amounts of harmful constituents that are permissible in brake friction components. Currently pending legislation in California (CA Senate Bill B 346) would prohibit the sale within the state of any motor vehicle brake friction materials containing specified constituents, such as for example copper, cadmium, lead, and mercury, in amounts that exceed certain concentrations. Safety is a concern as well, so pads made to comply with the new regulations must also meet applicable safety standards for braking performance, fade, and the like.